Many genes respond to environmental conditions, reacting to different environmental contexts in different ways. this characteristic of genes is called what

Our genes can be affected by the environment and change the way our traits are displayed, called the phenotype. However, changes in phenotype have an underlying genotypic source. Epigenetics or epigenetic changes are changes in the way traits are expressed as an effect of the environment (i.e. food we ate, chemicals in the body, environmental stresses), without changes in the DNA. Simply put, in epigenetics, some parts of the DNA are turned on or off in response to environmental conditions. 

Adaptatio

Although i don't know what is the simulated system, starfish are predators that eat mostly  microalgae,  snails, sponges, bivalves, mussels and other small marine animals. removing starfish from any system would definitely increase this animals that they prey.